NAME

SYNOPSIS

It is possible to have whitespace between a command line option and its
parameter.

DESCRIPTION

This manual page describes the GNU version of
eqn,
which is part of the groff document formatting system.
eqn
compiles descriptions of equations embedded within
troff
input files into commands that are understood by
troff.
Normally, it should be invoked using the
-e
option of
groff.
The syntax is quite compatible with Unix eqn.
The output of GNU
eqn
cannot be processed with Unix troff;
it must be processed with GNU troff.
If no files are given on the command line, the standard input
will be read.
A filename of
-
will cause the standard input to be read.

eqn
searches for the file
eqnrc
in the directories given with the
-M
option first, then in
/usr/lib/groff/site-tmac,
/usr/share/groff/site-tmac,
and finally in the standard macro directory
/usr/share/groff/1.19.2/tmac.
If it exists,
eqn
will process it before the other input files.
The
-R
option prevents this.

GNU
eqn
does not provide the functionality of neqn:
it does not support low-resolution, typewriter-like devices
(although it may work adequately for very simple input).

OPTIONS

-dxy

Specify delimiters
x
and~y
for the left and right end, respectively, of in-line equations.
Any
delim
statements in the source file overrides this.

-C

Recognize
.EQ
and
.EN
even when followed by a character other than space or newline.

The minimum point-size is~n.
eqn
will not reduce the size of subscripts or superscripts to
a smaller size than~n.

-Tname

The output is for device
name.
The only effect of this is to define a macro
name
with a value of~1.
Typically
eqnrc
will use this to provide definitions appropriate for the output device.
The default output device is
ps.

-Mdir

Search
dir
for
eqnrc
before the default directories.

-R

Don't load
eqnrc.

-fF

This is equivalent to a
gfont F
command.

-sn

This is equivalent to a
gsize n
command.
This option is deprecated.
eqn
will normally set equations at whatever the current point size
is when the equation is encountered.

-pn

This says that subscripts and superscripts should be
n~points smaller than the surrounding text.
This option is deprecated.
Normally
eqn
makes sets subscripts and superscripts at 70%
of the size of the surrounding text.

USAGE

Only the differences between GNU
eqn
and Unix eqn are described here.

Most of the new features of GNU
eqn
are based on TeX.
There are some references to the differences between TeX and GNU
eqn
below;
these may safely be ignored if you do not know TeX.

Automatic spacing

eqn
gives each component of an equation a type, and adjusts the spacing
between components using that type.
Possible types are:

ordinary

an ordinary character such as `1' or `x';

operator

a large operator such as
`Sigma';

binary

a binary operator such as `+';

relation

a relation such as `=';

opening

a opening bracket such as `(';

closing

a closing bracket such as `)';

punctuation

a punctuation character such as `,';

inner

a subformula contained within brackets;

suppress

spacing that suppresses automatic spacing adjustment.

Components of an equation get a type in one of two ways.

type t e

This yields an equation component that contains~e
but that has type~t,
where
t
is one of the types mentioned above.
For example,
times
is defined as

type "binary" \(mu

The name of the type doesn't have to be quoted, but quoting protects
from macro expansion.

chartype t text

Unquoted groups of characters are split up into individual characters,
and the type of each character is looked up;
this changes the type that is stored for each character;
it says that the characters in
text
from now on have type~t.
For example,

chartype "punctuation" .,;:

would make the characters `.,;:' have type punctuation
whenever they subsequently appeared in an equation.
The type~t
can also be
letter
or
digit;
in these cases
chartype
changes the font type of the characters.
See the
Fonts
subsection.

New primitives

e1 smallover e2

This is similar to
over;
smallover
reduces the size of
e1
and
e2;
it also puts less vertical space between
e1
or
e2
and the fraction bar.
The
over
primitive corresponds to the TeX
\over
primitive in display styles;
smallover
corresponds to
\over
in non-display styles.

vcenter e

This vertically centers
e
about the math axis.
The math axis is the vertical position about which characters
such as `+' and `-' are centered; also it is the vertical position
used for the bar of fractions.
For example,
sum
is defined as

{ type "operator" vcenter size +5 \(*S }

e1 accent e2

This sets
e2
as an accent over
e1.
e2
is assumed to be at the correct height for a lowercase letter;
e2
will be moved down according if
e1
is taller or shorter than a lowercase letter.
For example,
hat
is defined as

accent { "^" }

dotdot,
dot,
tilde,
vec,
and
dyad
are also defined using the
accent
primitive.

e1 uaccent e2

This sets
e2
as an accent under
e1.
e2
is assumed to be at the correct height for a character without a descender;
e2
will be moved down if
e1
has a descender.
utilde
is pre-defined using
uaccent
as a tilde accent below the baseline.

split stexts

This has the same effect as simply

text

but
text
is not subject to macro expansion because it is quoted;
text
will be split up and the spacing between individual characters
will be adjusted.

nosplit text

This has the same effect as

stexts

but because
text
is not quoted it will be subject to macro expansion;
text
will not be split up
and the spacing between individual characters will not be adjusted.

e opprime

This is a variant of
prime
that acts as an operator on~e.
It produces a different result from
prime
in a case such as
A opprime sub 1:
with
opprime
the~1
will be tucked under the prime as a subscript to the~A
(as is conventional in mathematical typesetting),
whereas with
prime
the~1
will be a subscript to the prime character.
The precedence of
opprime
is the same as that of
bar
and
under,
which is higher than that of everything except
accent
and
uaccent.
In unquoted text a~'
that is not the first character will be treated like
opprime.

special text e

This constructs a new object from~e
using a
troff(1)
macro named
text.
When the macro is called,
the string
0s
will contain the output for~e,
and the number registers
0w,
0h,
0d,
0skern,
and
0skew
will contain the width, height, depth, subscript kern, and skew of~e.
(The
subscript kern
of an object says how much a subscript on that object should be tucked in;
the
skew
of an object says how far to the right of the center of the object an
accent over the object should be placed.)
The macro must modify
0s
so that it will output the desired result with its origin at the current
point, and increase the current horizontal position by the width
of the object.
The number registers must also be modified so that they correspond to the
result.

For example, suppose you wanted a construct that `cancels' an expression
by drawing a diagonal line through it.

A positive value of the integer~n
(in hundredths of an em) sets the vertical spacing before the equation,
a negative value sets the spacing after the equation, replacing the
default values.
This primitive provides an interface to
groff's
\x
escape (but with opposite sign).

This keyword has no effect if the equation is part of a
pic
picture.

Extended primitives

col n { ... }

ccol n { ... }

lcol n { ... }

rcol n { ... }

pile n { ... }

cpile n { ... }

lpile n { ... }

rpile n { ... }

The integer value~n
(in hundredths of an em) increases the vertical spacing between rows,
using
groff's
\x
escape.
Negative values are possible but have no effect.
If there is more than a single value given in a matrix, the biggest one
is used.

Customization

The appearance of equations is controlled by a large number of parameters.
These can be set using
the
set
command.

set p n

This sets parameter~p
to value~n;
n~is an integer.
For example,

set x_height 45

says that
eqn
should assume an x~height of 0.45~ems.

Possible parameters are as follows.
Values are in units of hundredths of an em unless otherwise stated.
These descriptions are intended to be expository rather than
definitive.

minimum_size

eqn
will not set anything at a smaller point-size than this.
The value is in points.

fat_offset

The
fat
primitive emboldens an equation
by overprinting two copies of the equation
horizontally offset by this amount.

over_hang

A fraction bar will be longer by twice this amount than
the maximum of the widths of the numerator and denominator;
in other words, it will overhang the numerator and
denominator by at least this amount.

accent_width

When
bar
or
under
is applied to a single character,
the line will be this long.
Normally,
bar
or
under
produces a line whose length is the width of the object to which it applies;
in the case of a single character,
this tends to produce a line that looks too long.

delimiter_factor

Extensible delimiters produced with the
left
and
right
primitives will have a combined height and depth of at least this many
thousandths of twice the maximum amount by which the sub-equation that
the delimiters enclose extends away from the axis.

delimiter_shortfall

Extensible delimiters produced with the
left
and
right
primitives will have a combined height and depth
not less than the difference of
twice the maximum amount by which the sub-equation that
the delimiters enclose extends away from the axis
and this amount.

null_delimiter_space

This much horizontal space is inserted
on each side of a fraction.

script_space

The width of subscripts and superscripts is increased by this amount.

thin_space

This amount of space is automatically inserted after punctuation
characters.

medium_space

This amount of space is automatically inserted on either side
of binary operators.

thick_space

This amount of space is automatically inserted on either side of
relations.

x_height

The height of lowercase letters without ascenders such as `x'.

axis_height

The height above the baseline of the center of characters
such as `+' and `-'.
It is important that this value is correct for the font
you are using.

default_rule_thickness

This should set to the thickness of the
\(ru
character, or the thickness of horizontal lines produced with the
\D
escape sequence.

num1

The
over
command will shift up the numerator by at least this amount.

num2

The
smallover
command will shift up the numerator by at least this amount.

denom1

The
over
command will shift down the denominator by at least this amount.

denom2

The
smallover
command will shift down the denominator by at least this amount.

sup1

Normally superscripts will be shifted up by at least this amount.

sup2

Superscripts within superscripts or upper limits
or numerators of
smallover
fractions
will be shifted up by at least this amount.
This is usually less than sup1.

sup3

Superscripts within denominators or square roots
or subscripts or lower limits will be shifted up by at least
this amount.
This is usually less than sup2.

sub1

Subscripts will normally be shifted down by at least this amount.

sub2

When there is both a subscript and a superscript, the subscript
will be shifted down by at least this amount.

sup_drop

The baseline of a superscript will be no more
than this much amount below the top of the object on
which the superscript is set.

sub_drop

The baseline of a subscript will be at least this much below
the bottom of the object on which the subscript is set.

big_op_spacing1

The baseline of an upper limit will be at least this
much above the top of the object on which the limit is set.

big_op_spacing2

The baseline of a lower limit will be at least this
much below the bottom of the object on which the limit is set.

big_op_spacing3

The bottom of an upper limit will be at least this much above the
top of the object on which the limit is set.

big_op_spacing4

The top of a lower limit will be at least this much below
the bottom of the object on which the limit is set.

big_op_spacing5

This much vertical space will be added above and below limits.

baseline_sep

The baselines of the rows in a pile or matrix will normally be
this far apart.
In most cases this should be equal to the sum of
num1
and
denom1.

shift_down

The midpoint between the top baseline and the bottom baseline
in a matrix or pile will be shifted down by this much from the axis.
In most cases this should be equal to
axis_height.

column_sep

This much space will be added between columns in a matrix.

matrix_side_sep

This much space will be added at each side of a matrix.

draw_lines

If this is non-zero, lines will be drawn using the
\D
escape sequence, rather than with the
\l
escape sequence and the
\(ru
character.

body_height

The amount by which the height of the equation exceeds this
will be added as extra space before the line containing the equation
(using
\x).
The default value is 85.

body_depth

The amount by which the depth of the equation exceeds this
will be added as extra space after the line containing the equation
(using
\x).
The default value is 35.

nroff

If this is non-zero,
then
ndefine
will behave like
define
and
tdefine
will be ignored,
otherwise
tdefine
will behave like
define
and
ndefine
will be ignored.
The default value is~0
(This is typically changed to~1 by the
eqnrc
file for the
ascii,
latin1,
utf8,
and
cp1047
devices.)

A more precise description of the role of many of these
parameters can be found in Appendix~H of
The TeXbook.

Macros

Macros can take arguments.
In a macro body,
$n
where
n
is between 1 and~9,
will be replaced by the
n-th
argument if the macro is called with arguments;
if there are fewer than
n~arguments, it will be replaced by nothing.
A word containing a left parenthesis where the part of the word
before the left parenthesis has been defined using the
define
command
will be recognized as a macro call with arguments;
characters following the left parenthesis
up to a matching right parenthesis will be treated as comma-separated
arguments;
commas inside nested parentheses do not terminate an argument.

sdefine name X anything X

This is like the
define
command, but
name
will not be recognized if called with arguments.

include sfiles

copy sfiles

Include the contents of
file
(include
and
copy
are synonyms).
Lines of
file
beginning with
.EQ
or
.EN
will be ignored.

ifdef name X anything X

If
name
has been defined by
define
(or has been automatically defined because
name
is the output device)
process
anything;
otherwise ignore
anything.
X
can be any character not appearing in
anything.

undef name

Remove definition of
name,
making it undefined.

Besides the macros mentioned above, the following definitions are available:
Alpha,
Beta,
...,
Omega
(this is the same as
ALPHA,
BETA,
...,
OMEGA),
ldots
(three dots on the base line),
and
dollar.

Fonts

eqn
normally uses at least two fonts to set an equation:
an italic font for letters,
and a roman font for everything else.
The existing
gfont
command
changes the font that is used as the italic font.
By default this is~I.
The font that is used as the roman font can be changed
using the new
grfont
command.

grfont f

Set the roman font to~f.

The
italic
primitive uses the current italic font set by
gfont;
the
roman
primitive uses the current roman font set by
grfont.
There is also a new
gbfont
command, which changes the font used by the
bold
primitive.
If you only use the
roman,
italic
and
bold
primitives to changes fonts within an equation,
you can change all the fonts used by your equations
just by using
gfont,
grfont
and
gbfont
commands.

You can control which characters are treated as letters
(and therefore set in italics) by using the
chartype
command described above.
A type of
letter
will cause a character to be set in italic type.
A type of
digit
will cause a character to be set in roman type.

FILES

u+2n

/usr/share/groff/1.19.2/tmac/eqnrc
Initialization file.

BUGS

Inline equations will be set at the point size that is current at the
beginning of the input line.